Real-time traffics, such as automatic driving and industrial automatic control, etc., that will be carried out in a next-generation mobile communications network, have a very high requirement on transmission latency, such as requiring that peer-to-peer latency is between 1 ms and 10 ms. When such traffics are carried by an LTE system, a relatively large challenge will be brought about to latency performance of the network. And furthermore, for a legacy transmission control protocol (TCP) traffic, reduction of peer-to-peer latency may greatly improve throughput of the system. Considering from the two aspects, it is urgently needed to lower the peer-to-peer latency of the traffics in the LTE system.
3GPP (3rd-generation partnership project) has been working on the reduction of peer-to-peer latency by shortening a TTI. A legacy user equipment (UE) adopts 1 ms as the TTI with the same value of a subframe, that is, a basic time unit of scheduling data is 1 ms. If a shortened TTI is supported in a UE in the latest release, such as a TTI of 0.5 ms or shorter, peer-to-peer latency of a traffic will be outstandingly lowered. A round trip time (RTT) in a legacy system is 8 TTIs. And after the TTIs are shortened, the RTT will become from original 8 ms to 4 ms, or even shorter.
Hence, a legacy UE (for example, the UE adopts 1 ms as the TTI) and a shorter TTI UE (for example, the UE adopts a TTI shorter than 1 ms) will exist in an LTE cell. And backward compatibility needs to be kept in the design of an LTE system, so as to ensure that the legacy UE and the shorter TTI UE operate at the same time while not interfering with each other.
It should be noted that the above description of the background is merely provided for clear and complete explanation of this disclosure and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background of this disclosure.